Examine the stages a medium-sized star such as the
sun goes through as it begins to run out of hydrogen
in its core.

! Click
the With Labels or Without Labels buttons
to see an animation of diagrams that represent the life
stages of average stars. Use the movie controls to examine
different parts of the sequence and read the text associated
with each phase.

5. Describe how a medium-sized star can
grow as it runs out of hydrogen fuel.

6. How is the formation of a planetary
nebula different from a supernova?